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Hi Mariana,
Yes, you're right. My feeling is that it could be
implementation dependent, but not sure right now.
Definitively we need to work more on
this.
Regards,
Jordi
----- Original Message -----
Sent: Thursday, November 13, 2003 11:00
AM
Subject: Comment on
draft-palet-v6ops-proto41-nat-03.txt
Hi Jordi,
I have a comment on the following paragraph in Section
5 of your draft
"6to4
and Proto-41 forwarding can coexist in the same NAT box. In that case,
an IPv6 over IPv4 packet received, will be forwarded to the private LAN only
if the IPv6 destination does not belong to the local 6to4 /48 prefix.
Otherwise it will be decapsulated in the NAT box, following 6to4 procedures.
This fact avoids the problems created by mobile users when they visit a
network that uses 6to4, in the case they have some automatic proto-41 setup.
"
Let's analyze how a router works
when it's simultaneously supports 6to4 and proto-41 mechanisms as you
proposed above.
If there is an
proto-41 entity such as (source IPv4 address, target IPv4 address, ID=41) in
the NAT table of the router, then the so called prerouting is done for
all packets matching this entity. Note, this is the first action taken by the
router before any other actions are taken. With other words, the router
forwards all incoming IPv4 packets with PF=41 to the target IPv4 address
before even decapsulating them and looking what the IPv6 dest address is.
So, what is written above "an IPv6 over IPv4 packet received, will be forwarded to the private LAN
only if the IPv6 destination does not belong to the local 6to4 /48
prefix. Otherwise it will be decapsulated in the NAT box, following 6to4
procedures." does not work in
practice, because it require that the router first decapculates and
looks the IPv6 dest. ad! dress.
Summing up, I do see that 6to4 and proto-41 can coexist n the same NAT
box but rather as two separate modes, i.e. the router can switch between 6to4
and proto-41 depending of certain preferences as the default one is 6to4 for
example. In fact, I see the applicability of proto-41 in IPv4-only NAT
boxes, but if the latter are upgraded to 6to4 routers it seems to me overdone
to keep proto-41 as well.
Greetings,
Mariana
-----------------------------------------------------------------------------------------------------------------
Dr.
Mariana Nikolova
Philips Research Laboratories Eindhoven
(IST/SwA/DS)
Prof. Holstlaan 4, 5656 AA, Eindhoven, The
Netherlands
room: WDC 1.35, phone: +31-40-27-45455
e-mail:
mariana.nikolova@philips.com
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